Apex seal assembly of a rotary piston engine

ABSTRACT

An apex seal assembly which has combined apex seal members with at least one side at an angle expanding toward the lower portion of the side surface and an arcuate spring of U-shape in section to hold the members together and in contact with the inner wall of a rotary piston engine.

United States Patent Sakamaki Dec. 25, 1973 APEX SEAL ASSEMBLY OF AROTARY 3,238,929 3/1966 Brodbeck et a1. 418/122 x PISTON ENGINE3,263,912 8/1966 Frenzel 3,280,801 10/1966 Scherenberg 418/122 X [75]Inventor: Hiroshi Sakamaki, Tochigi, Japan [7 3] Assignee: Nippon PistonRing Co., Ltd.,

T k Japan Primary Examiner-Al Lawrence Smith Assistant Examiner--RichardSher [22] led: 1972 Att0rney-Richard C. Sughrue et a1.

[21] Appl. No.: 233,688

[30] Foreign Application Priority Data Mar. 12, 1971 Japan 46/13586 [57]ABSTRACT 52 U.S. c1. 418/117, 418/122 An p seal assembly which hascombined pe Seal 51 1m. (:1. F01c 19/02 members with at least one sideat an angle expanding [58] Field of Search 418/122, 123, 117; toward thelower portion of the side Surface and an 277/81 p arcuate spring ofU-shape in section to hold the members together and in contact with theinner wall of a [56] References Cited rotary Piston engine- UNITEDSTATES PATENTS 3,159,336 12/1964 Paschke 418/122 X 4 Claims, 12 DrawingFigures APEX SEAL ASSEMBLY OF A ROTARY PISTON ENGINE BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a rotarypiston engine, and more particularly to an apex seal assembly for arotary piston engine. I

2. Description of the Prior Art The apex seals mounted at the respectivecorners of the rotor of the rotary piston engine for sealing the workfluid in contact with the inner peripheral surface of a two or morelobed center housing of the rotary piston engine are known per se. Inorder to maintain airtightness in the rotary piston engine, therespective apex seals mounted at the corners of the rotor of the rotarypiston engine are strongly urged into contact with the inner peripheralsurface of the two or more lobed center housing by springs provided atthe back side of the apex seals. Centrifugal force of therotor uponrotation and gas pressure of the work fluid in the combustion chamber ofthe rotary piston engine, etc., also contribute to maintaining the seal.For this reason, the inner peripheral surface of the two or more lobedcenter housing and the apex seals are subject to severe wear and furtherthe inner peripheral surfaces of the center housing of the rotary pistonengine tends to be abnormally worn by the rotating contact of the apexseals. The primary causes of such abnormal wear of these components ofthe rotary piston engine are many and various, but the particular noteis the wearing force as a result of the apex seal being urged more thannecessary onto the inner peripheral surface of the two or more lobedcenter housing acting on the apex seal assembly. And, the greater themass of the apex seal, the larger the wearing force becomes.Accordingly, it is considered that the foremost cause of such abnormalwear is due to the mass of the apex seal. From this fact, the mass ofthe apex seal should be made small, and yet it is strongly desired tohave wear resistance and mechanical strength.

As a result of studies of the apex seal made of carbon alloy, the massof the apex seal has been reduced but the mechanical strength of theapex seals is low because it is very brittle. In order to improve themechanical strength of the apex seal, it is most desirable that the apexseal be made of metals such as cast iron, steel, etc. This howevercauses the mass of the apex seal to become large with the result thatpresent apex seals are not made of metal.

' SUMMARY or THE INVENTION It is, therefore, one object of the presentinvention to provide an apex seal assembly which is superior in wearresistance and mechanical strength while still being relatively low inmass.

It is another object of the present invention to provide an apex sealassembly which is not worn abnormally on the inner peripheral surface ofthe two or more lobed center housing.

According to one aspect of the present invention, there is provided anapex seal assembly which comnrises combined apex seals having an angleexpanding toward the lower portion of the side surface of at least oneside thereof with an arcuate spring of U shape in section to hold theseals together and against the inner peripheral surface.

These and other objects, features and advantages of the presentinvention will become apparent from the following description taken inconjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofa rotary piston enginemounted with the conventional apex seals;

FIG. 2 is a perspective view of an apex seal for the explanatory purposeof the apex seal of the present invention;

FIG. 3 is a partial enlarged longitudinal sectional view of the apexseal shown in FIG. 2 mounted in the apex seal groove of the rotor of therotary piston engine;

FIG. 4 is an enlarged longitudinal sectional view of one embodiment ofthe apex seal of this invention;

FIG. 5 is an enlarged longitudinal sectional view f another embodimentof the apex seal according to the present invention;

FIGS. 6 and 7 are partial enlarged longitudinal sectional views of theapex seal of this invention shown in FIG. 4, mounted in the apex sealgroove;

FIG. 8 isa partial enlarged longitudinal sectional view of the presentinvention shown in FIG. 5 mounted in the wedged apex seal groove of therotor of the rotary piston engine;

FIGS. 9 and 10 are plan and side views of one embodiment of the springfor apex seal used in the apex seal assembly of the present invention;

FIG. 11 is a sectional view of the combined apex seal with spring shownin FIG. 9 taken along the'line XI-XI in FIG. 9 of the present invention;and

FIG. 12 is a plan view of another embodiment of the spring used in theapex seal assembly of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to clearly understandthe apex seal assembly of the present invention, the conventional apexseal ill now be described at first with reference to FIG. 1 which showsthe rotary piston engine mounted with the conventional apex sealsthereto.

In order to hold the air-tightness or sealing sufficiently in therotarypiston engine, the apex seals 2 mounted at the corners of therotor 4 of the rotary piston engine are strongly urged in contact withthe inner peripheral surface 51 of the two or more lobed center housing5 by the springs 3 provided at the back side of the apex seals 2,centrifugal force of the rotor 4 upon rotation and gas pressure of thework fluid in the combustion chamber of the rotary piston engine, etc.For this reason, the inner peripheral surface 51 of the two or morelobed center'hosuing 5 and the apex seals 2 are severely worn, andfurther the inner peripheral surfaces 51 of the center housing 5 of therotary piston engine tend to be abnormally worn by the rotationalcontact with the apex seals 2. The primary causes of such abnormal wearof these components of the rotary piston engine are many, but ofparticular note is the wearing force as a result of the apex seal 2being urged more than necessary onto the inner peripheral surface 51 ofthe center housing 5 acting on the apex seal assembly.

The present invention overcomes the conventional disadvantages of theapex seal by a particular structure of the apex seal with respect to themassive metal apex seals to provide novel apex seals.

Reference is now made to the drawings, particularly to FIGS. 2 and 3,which show the special structure of the apex seal mounted in the apexseal groove of the rotor of the rotary piston engine. The embodimentshown in FIGS. 2 and 3 incorporates one of the features of thisinvention, namely the use of two seal members. The seal members 6 and 7have sliding surfaces 60 and 70, respectively, of semi-circular sectionas shown in FIGS. 2 and 3 to provide a combined apex seal 8. Thefrictional force of the apex seal 2 contacting the inner peripheralsurface 51 of a two or more lobed center housing 5 due to thecentrifugal force, is approximately one-half that of the single apexseal made of the same material. The result is that the frictional forcedue to the massive apex seal is lessened to be equal to the less massiveapex seal made of less massive material.

As a result of experimentation it has been found that the combined apexseal 8 tends to be adhered onto the apex seal groove of the rotor of therotary piston engine by the carbon slag on all the surfaces of the apexseal groove and both side surfaces of the apex seals. The carbon slag isproduced by the combustion of lubricating oil, etc.

Further, as shown in FIG. 3, it is impossible with the conventionalspring 3 to independently follow the seal members 6 and 7 of thecombined apex seal 8 with the inner wall of the center housing of therotary piston engine. Therefore, the present invention eliminates suchtrouble by providing an apex seal assembly of a rotary piston enginewhich has combined apex seals 8 provided with an angle expanding towardthe lower portion of the side surface of at least one side thereof andan arcuate spring of U shape in section.

Referring now to FIG. 4, which shows one embodiment of the apex sealconstructed according to the present invention, an angle expandingtoward the lower portion of both side surfaces 61, 62 and 71, 72 of theseal members 6 arid 7 is provided. In other words, an acute angle isformed between the side surface of the seal member and a line parallelto the axis of the seal member. The angle is formed at the upper portionof the seal member such that the distance between the side surface andthe parallel line increases at the lower portion of the seal member. Theseal members 6 and 7 are combined to provide a combined apex seal 81.FIG. shows another embodiment of the apex seal constructed according tothe present invention wherein an angle 6 expanding toward the lowerportions of both side surfaces 61 and 72 of the seal mem bers 6 and 7'isprovided to form a combined apex seal 82 which eliminates the adhesionof the apex seals on the apex seal groove. More particularly, the sealmembers 6 and 7 having angles 0 on at least one of their side surfacesare combined to provide a combined apex seal 7 In operation, thecombined apex seal 81 is mounted in the rectangular apex seal groove 9provided on the corner of the rotor 4 together with the spring 31, asshown in FIG. 6. The apex seal of this invention is mounted in the apexseal groove of the rotor of the rotary piston engine. The combined apexseal 81 is disposed at the side surface 91 of the rectangular apex sealgroove 9 at the intake and exhaust strokes. It is disposed at the sidesurface 92 of the rectangular apex seal groove at the ignition,expansion and compression strokes as shown in FIG. 7. Thus, the combinedapex seal is repeatedly moved. Arrows A shown in FIGS. 6, 7 and 8indicate the rotating direction of the rotor 4.

Since the combined apex seal 81 has an angle 0 expanding toward thelower portion of the seal members 6 and 7, the moving amount of thelower portions of the seal members 6 and 7 is longer than the upperportions thereof. Therefore, since there is such movement of the sealmembers 6 and 7, the aforementioned carbon slag is pulverized therebypreventing the apex seal and the apex seal groove from adhering.

FIG. 8 shows the apex seal mounted in the wedged apex seal groove of therotor of the rotary piston engine. The combined apex seal 82 is mountedtogether with spring 31 in the wedged apex seal groove 91 provided atthe corner of the rotor 4.

In operation of the apex seal shown in FIG. 8, the side clearance C isvaried every time the combined apex seal 82 follows the inner wall 5 ofthe center housing of the rotary piston engine. When the clearance C isvaried, the carbon slag is pulverized according to the movement of thecombined apex seal in the apex seal groove so as to prevent the adhesionthereof.

Experimentation has shown that the angle 0 expanding toward the lowerportion of the seal members 6 and 7 is most preferable if the width Bdesignated in FIGS. 4 and 5 is 50 to 500 microns.

The apex seal assembly of the present invention also comprises a springcombined with the thus constructed combined apex seal. Since the sealmembers 6 and 7 are combined to provide the combined apex seal 81, theseal members 6 and 7 of the combined apex seal 81 are required toindependently follow the inner wall 5 of the center housing of therotary piston engine.

The spring is used for the combined apex seal so as to independentlyfollow the respective seal members 6 and 7 of the combined apex sealwith respect to the inner wall 51 of the center housing 5. Moreparticularly, as shown in FIGS. 9, l0 and 11, which show the spring usedtogether with the apex seal used in the apex seal assembly, the spring31 is arcuate of U shape in section. As thus constructed, the uppersurfaces 311 and 312 are formed thereon for causing contacting underpressure with the seal members 6 and 7 of the combined apex seal 81.This allows the seal members to independently follow in contact with theinner peripheral surface under pressure of the center housing of therotary piston engine.

Reference is now made to FIG. 12, which shows another embodiment of thespring used together with the apex seal assembly of the presentinvention. Slits 314 are nonsymmetrically and alternatively provided onthe spring 31 from longitudinal edges 311 and 312 of both sides withrespect to the longitudinal central line m-m. This arrangement isadvantageous in the following property of the respective seal memberswith the inner wall of the center housing.

Thus, when the spring 31 is used together with the combined apex seal, amore effective seal is formed.

It should be understood from the foregoing description that the apexseal of this invention is made of metal so as to provide superior wearresistance and mechanical strength and the massive structure iseliminated by the combined two individual members of the apex seal.Further, the apex seal has an angle expanding toward the lower portionsof the seal members so as to also eliminate the adhesion of the apexseal to the apex seal groove.

It should also be understood that since the spring is combined with thecombined apex seal, the seal members independently follow the inner wallof the center housing under pressure and the apex seal assembly operatesmore effectively.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. An apex seal assembly for a rotary piston engine having a radial sealgroove in the rotor of said engine, said seal assembly comprising:

a. at least two seal members within said groove, each seal member havinga curved contact surface and two flat side surfaces, a line coincidingwith at least one side surface forming an acute angle with thetravsverse axis of said seal member, said acute angle being locatedradially inwardly of said seal member, whereby said seal membercontinuously tapers from its contact surface toward its radial innerend; and

b. a U shaped arcuate spring within said groove having ends contactingthe inner ends of the respective seal members for forcing said sealmembers against the inner peripheral surface of the housing of saidengine.

2. The apex seal assembly as set forth in claim 1 wherein an acute angleis formed by said transverse axis and respective lines coinciding witheach of said side surfaces.

3. The apex seal assembly as set forth in claim 1 wherein said sealgroove is wedged shaped.

4. The apex seal assembly as set forth in claim 1 wherein said springhas a plurality of slits formed therein.

1. An apex seal assembly for a rotary piston engine having a radial sealgroove in the rotor of said engine, said seal assembly comprising: a. atleast two seal members within said groove, each seal member having acurved contact surface and two flat side surfaces, a line coincidingwith at least one side surface forming an acute angle with thetravsverse axis of said seal member, said acute angle being locatedradially inwardly of said seal member, whereby said seal membercontinuously tapers from its contact surface toward its radial innerend; and b. a U shaped arcuate spring within said groove having endscontacting the inner ends of the respective seal members for forcingsaid seal members against the inner peripheral surface of the housing ofsaid engine.
 2. The apex seal assembly as set forth in claim 1 whereinan acute angle is formed by said transverse axis and respective linescoinciding with each of said side surfaces.
 3. The apex seal assembly asset forth in claim 1 wherein said seal groove is wedged shaped.
 4. Theapex seal assembly as set forth in claim 1 wherein said spring has aplurality of slits formed therein.